The present invention relates generally to fastener driving tools such as pneumatic tools, cordless framing and trim tools and the like. More particularly, the present invention relates to an adjustable depth-of-drive mechanism for a fastener driving tool.
As exemplified in U.S. Pat. No. 6,543,644, which is incorporated by reference, fastening tools, and particularly pneumatic framing tools for use in driving fasteners into workpieces, are described. Such fastener driving tools are commercially available from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill.
Such tools incorporate a housing enclosing an air pressure cylinder. Slidably mounted within the cylinder is a piston assembly that divides the cylinder into a drive chamber on one side of the piston assembly and a return chamber on the opposite side thereof. The piston assembly includes a piston head and a rigid driver blade that is disposed within the cylinder. A movable valve plunger is oriented above the piston head.
Upon the pulling of a trigger, a trigger valve closes and opens a passageway to the atmosphere. At this point, the air pressure in the drive chamber is higher than that in the return chamber, causing the piston and driver blade to be actuated downward to impact a positioned fastener and drive it into the workpiece. Fasteners are fed into the nosepiece from a supply assembly, such as a magazine, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
As the piston is actuated downward, it drives the air inside the cylinder through a series of holes into the return air chamber. After the trigger is released, compressed air pushes the valve plunger back into place, blocking the airflow to the piston head. At this time, there is no downward pressure, so the compressed air in the return chamber can push the piston head back up. The air above the piston head is forced out of the tool and into the atmosphere.
Although a pneumatic framing tool has been described above, other types of fastener driving tools, such as combustion, powder activated and/or electrically powered tools are well known in the art, and are also contemplated for use with the present depth-of-drive adjustment mechanism.
One operational characteristic required in fastener driving applications is the ability to predictably control fastener driving depth. For the sake of appearance, some applications require fasteners to be countersunk below the surface of the workpiece, others require the fastener to be driven flush with the surface of the workpiece, and some may require the fastener to stand off above the surface of the workpiece. Depth adjustment has been achieved in pneumatically and combustion powered tools through a tool controlling mechanism, referred to as a drive probe, that is movable in relation to the nosepiece of the tool. The range of movement of the drive probe typically defines a range for fastener depth of drive.
One disadvantage of previous depth adjusting mechanisms is that they allow only one type of adjustment, usually gross adjustment. In this mode, a lock is released and the drive probe moves relatively freely relative to the nosepiece. Once the desired adjustment is achieved, the probe is locked in position. Many projects require the user to accurately set the depth of drive at a specific measurement. This can be difficult to accomplish when the adjusting mechanism only allows for gross adjustments, and therefore the user may have to adjust the depth of drive several times through trial and error in order to obtain the correct measurement for the depth of drive.
In other tools, the only type of adjustment offered is fine adjustment, which is provided using a biased detent engaging a rotating adjuster or barrel. However, many such systems have been known to lose their desired position over periods of extended use due to repeated tool impact.
Accordingly, there is a need for a single depth-of-drive adjustment mechanism for use in a fastener driving tool that allows the user the option of adjusting the mechanism in both a fine or a gross adjustment setting.
There also exists a need to provide a depth-of-drive mechanism for a fastener driving tool that is easily accessible and that can be manipulated by both experienced construction workers, contractors and laymen alike.
Further, there exists a need for a depth-of-drive mechanism that is strong enough to maintain its adjustment positioning despite repeated tool impact.